Evaluation of Hybrid Response to Seeding Rate

Rationale and Objective

  • Research has consistently shown that corn yield response to plant population differs among hybrids as well as yield levels, with more productive soils generally having a higher optimal population.
  • Increased usage of variable-rate seeding technology provides the opportunity to vary the population of each hybrid according to soil productivity level within a field.
  • This study was conducted to evaluate yield response of several hybrids to plant population at different yield levels, with the goal of determining optimal population and the potential value of variable-rate seeding for each hybrid.

Corn at 30,000 (left) vs. 38,000 plants/acre (right). Note the reduction in sunlight reaching the soil surface at the higher density.

Study Description

Locations: 27 in central and eastern Missouri 
Plot Layout:  Field-length strips 
Populations:   30,000, 34,000 and 38,000 plants/acre. 
Hybrids:    4 per location   
  Pioneer® Hybrids/Brands¹:      
  P0365YHR (YGCB, HX1, LL, RR2)      P0636HR (HX1, LL, RR2)  
  P0993HR (HX1, LL, RR2)      P1248AM™ (AM, LL, RR2)  
  P1522HR (HX1, LL, RR2)      P1690HR (HX1, LL, RR2) 
  • Yield monitor data from these plots were analyzed in Pioneer® Field360™ Studio software to remove common sources of yield monitor error. 


  • Average corn yield across all hybrids and yield levels was significantly affected by plant population (p<0.05).
  • Yield increased linearly with population, with the greatest average yield at 38,000 plants/acre.
  • Plant population response of individual hybrids differed among yield levels.
  • In general, yield of the earlier maturity hybrids (Pioneer® hybrids P0365YHR, P0636HR, P0993HR, and Pioneer® P1248AM™ brand corn) differed little across plant populations at the lowest yield level (<120 bu/acre) (similar response observed in 2012).
  • At higher yield levels, there were varying responses by these hybrids to plant population.
  • All 4 early CRM hybrids have excellent drought tolerance, which may explain their yield stability at 38,000 plants/acre.
  • Another possible contributing factor may be quicker and greater shading of the soil at higher plant density, which may help reduce evaporative loss from the soil surface (see photo).
  • Yield of the later maturity hybrids (P1522HR and P1690HR) tended to decrease at 38,000 plants/acre in <200 bu/acre yield environments.
    • The 30,000 plants/acre population resulted in the highest yield in 120-160 bu/acre yield environments for both of these hybrids. 
    • Yield response to population varied among hybrids in 160-200 bu/acre and 200 bu/acre yield environments.
  • In general, hybrid response to plant population varied the most in the middle yield ranges, especially among the earlier maturity hybrids. This could be due to variables, such as ear flex ability, kernel depth, test weight, etc., expressed more at these yield levels. 

Variable-Rate Seeding Implications

  1. Variation in hybrid response to plant population at different yield levels observed in this study confirms the importance of tailoring variable-rate seeding plans to individual products.
  2. Hybrids with a higher level of drought tolerance may not require a drastic reduction in population in the lower yielding areas of a field.
  3. Later maturity hybrids with lower stress tolerance may be more likely to benefit from variable-rate seeding.  They have the potential to provide a larger response to varying populations in low- and high-yielding areas of the field.
  4. Consult your Pioneer sales professional for variable-rate seeding suggestions.

AM - Optimum® AcreMax® Insect Protection system with YGCB, HX1, LL, RR2. Contains a single-bag integrated refuge solution for above-ground insects. In EPA-designated cotton growing counties, a 20% separate refuge must be planted with Optimum AcreMax products.


YGCB,HX1,LL,RR2 (Optimum® Intrasect®) - Contains the YieldGard® Corn Borer gene and Herculex® I gene for resistance to corn borer.
Herculex® I Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logo are registered trademarks of Dow AgroSciences LLC.
YieldGard®, the YieldGard Corn Borer Design and Roundup® Ready are registered trademarks used under license from Monsanto Company.
Liberty®, LibertyLink® and the Water Droplet Design are trademarks of Bayer.